U.S. patent application number 15/894512 was filed with the patent office on 2018-06-14 for dual-direction collimator.
The applicant listed for this patent is LEIA INC.. Invention is credited to David A. Fattal, Xuejian Li, Ming Ma.
Application Number | 20180164489 15/894512 |
Document ID | / |
Family ID | 58188550 |
Filed Date | 2018-06-14 |
United States Patent
Application |
20180164489 |
Kind Code |
A1 |
Fattal; David A. ; et
al. |
June 14, 2018 |
DUAL-DIRECTION COLLIMATOR
Abstract
Dual-direction collimation and a dual-direction optical
collimator provide dual-direction collimated light at a non-zero
propagation angle. The dual-direction collimator includes a
vertical collimator configured to collimate light in a vertical
direction and a horizontal collimator configured to collimate the
vertically collimated light in a horizontal direction. The
horizontal collimator is located at an output of the vertical
collimator. A three-dimensional (3D) display includes the
dual-direction collimator, a plate light guide and an array of
multibeam diffraction gratings at a surface of the plate light
guide to couple out the dual-direction collimated light guided in
the plate light guide as a plurality of light beams corresponding
to different 3D view of the 3D electronic display.
Inventors: |
Fattal; David A.; (Mountain
View, CA) ; Ma; Ming; (Palo Alto, CA) ; Li;
Xuejian; (Menlo Park, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LEIA INC. |
Menlo Park |
CA |
US |
|
|
Family ID: |
58188550 |
Appl. No.: |
15/894512 |
Filed: |
February 12, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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PCT/US2015/056529 |
Oct 20, 2015 |
|
|
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15894512 |
|
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62214978 |
Sep 5, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 6/0046 20130101;
G02B 19/0047 20130101; G02B 6/0031 20130101; G02B 6/0068 20130101;
G02B 6/0058 20130101; G02B 6/0038 20130101; G02B 19/0023 20130101;
G02B 27/30 20130101; G02B 6/0023 20130101; G02B 6/0078 20130101;
G02B 5/18 20130101; G02B 30/00 20200101 |
International
Class: |
F21V 8/00 20060101
F21V008/00; G02B 27/30 20060101 G02B027/30; G02B 27/22 20060101
G02B027/22 |
Claims
1. A dual-direction optical collimator comprising: a vertical
collimator configured to collimate light in a vertical direction;
and a horizontal collimator configured to collimate light in a
horizontal direction substantially orthogonal to the vertical
direction, the horizontal collimator being located adjacent to an
output of the vertical collimator to horizontally collimate
vertically collimated light from the vertical collimator to provide
dual-direction collimated light at an output of the dual-direction
optical collimator, wherein the dual-direction optical collimator
is configured to provide the dual-direction collimated light at a
non-zero propagation angle relative to a horizontal plane
corresponding to the horizontal direction.
2. The dual-direction optical collimator of claim 1, wherein the
vertical collimator comprises an optical reflector having a
parabolic shape and a tilt angle, the tilt angle being configured
to provide the non-zero propagation angle of the dual-direction
collimated light.
3. The dual-direction optical collimator of claim 1, wherein the
horizontal collimator comprises an optical reflector having a
parabolic shape, the optical reflector being configured to
substantially span an output aperture of the dual-direction optical
collimator, the dual-direction collimated light to have a
substantially uniform distribution across the output aperture.
4. The dual-direction optical collimator of claim 1, wherein the
horizontal collimator comprises an optical reflector having a
plurality of sub-reflectors configured in combination to
substantially span an output aperture of the dual-direction optical
collimator, each sub-reflector comprising a parabolic-shaped
reflective surface.
5. The dual-direction optical collimator of claim 4, wherein the
optical reflector is a Fresnel reflector.
6. The dual-direction optical collimator of claim 4, wherein a
first sub-reflector of the plurality of sub-reflectors is
configured to receive the vertically collimated light from a first
vertical collimator located at a first edge of the horizontal
collimator, a second sub-reflector of the plurality of
sub-reflectors being configured to receive the vertically
collimated light from a second vertical collimator located at a
second edge of the horizontal collimator, the second edge being
opposite the first edge in the horizontal plane corresponding to
the horizontal direction.
7. The dual-direction optical collimator of claim 1, wherein the
vertical collimator is integral to and comprises a material of the
horizontal collimator.
8. A backlight comprising the dual-direction optical collimator of
claim 1, the backlight further comprising: a plate light guide
coupled to the output of the dual-direction optical collimator, the
plate light guide being configured to receive and to guide the
dual-direction collimated light at the non-zero propagation angle,
wherein the plate light guide is further configured to emit a
portion of the guided, dual-direction collimated light from a
surface of the plate light guide.
9. The backlight of claim 8, further comprising a light source
configured to provide light to the dual-direction optical
collimator, the light source being located adjacent to the vertical
collimator and being configured to provide the light to an input of
the vertical collimator.
10. The backlight of claim 9, wherein the light source comprises a
plurality of different optical sources configured to provide
different colors of light, the different optical sources being
offset from one another, wherein the offset of the different
optical sources is configured to provide different, color-specific,
non-zero propagation angles of the dual-direction collimated light
corresponding to each of the different colors of light.
11. The backlight of claim 8, further comprising a multibeam
diffraction grating configured to diffractively couple out a
portion of the guided, dual-direction collimated light from the
plate light guide as a plurality of light beams emitted from the
plate light guide surface, a light beam of the light beam plurality
having a principal angular direction different from principal
angular directions of other light beams of the light beam
plurality.
12. A three-dimensional (3D) electronic display comprising the
backlight of claim 11, the 3D electronic display further
comprising: a light valve to modulate a light beam of the light
beam plurality, the light valve being adjacent to the multibeam
diffraction grating, wherein the principal angular direction of the
light beam corresponds to a view direction of the 3D electronic
display, the modulated light beam representing a pixel of the 3D
electronic display in the view direction.
13. A three-dimensional (3D) electronic display comprising: a
dual-direction optical collimator comprising a vertical collimator
and a horizontal collimator located adjacent to an output of the
vertical collimator, the dual-direction optical collimator being
configured to provide dual-direction collimated light having both
vertical collimation and horizontal collimation at a non-zero
propagation angle relative to a horizontal plane; a plate light
guide configured to guide the dual-direction collimated light as a
guided light beam at the non-zero propagation angle; and an array
of multibeam diffraction gratings at a surface of the plate light
guide, a multibeam diffraction grating of the array being
configured to diffractively couple out a portion of the guided
light beam as a plurality of coupled-out light beams having
different principal angular directions corresponding to directions
of different 3D views of the 3D electronic display.
14. The 3D electronic display of claim 13, wherein the vertical
collimator comprises an optical reflector having a parabolic shape
and a tilt angle, the tilt angle being configured to determine the
non-zero propagation angle of the dual-direction collimated light
at an output of the dual-direction optical collimator.
15. The 3D electronic display of claim 13, wherein the horizontal
collimator comprises an optical reflector having a parabolic shape,
the optical reflector of the horizontal collimator being configured
to substantially span an output aperture of the dual-direction
optical collimator and to provide the dual-direction collimated
light with a substantially uniform distribution across the output
aperture.
16. The 3D electronic display of claim 13, wherein the horizontal
collimator has a first edge and a second edge that is opposite the
first edge, the horizontal collimator comprising an optical
reflector that comprises a plurality of sub-reflectors configured
in combination to substantially span an output aperture of the
dual-direction optical collimator, a first sub-reflector of the
sub-reflector plurality being configured to receive vertically
collimated light from a first vertical collimator at the first edge
of the horizontal collimator, a second sub-reflector of the
sub-reflector plurality being configured to receive vertically
collimated light from a second vertical collimator at the second
edge of the horizontal collimator.
17. The 3D electronic display of claim 13, wherein the array of
multibeam diffraction gratings comprises a chirped diffraction
grating having curved diffractive features.
18. The 3D electronic display of claim 17, wherein the chirped
diffraction grating is a linear chirped diffraction grating.
19. The 3D electronic display of claim 13, further comprising: a
light source configured to provide light to an input of the
dual-direction optical collimator; and a light valve array
configured to selectively modulate the coupled-out light beams of
the plurality as 3D pixels corresponding to the different 3D views
of the 3D electronic display.
20. The 3D electronic display of claim 19, wherein the light valve
array comprises a plurality of liquid crystal light valves.
21. The 3D electronic display of claim 19, wherein the light source
comprises a plurality of different light emitting diodes (LEDs)
configured to provide different colors of light, the different LEDs
being offset from one another, wherein the offset of the different
LEDs is configured to provide different, color-specific, non-zero
propagation angles of the dual-direction collimated light, a
different, color-specific, non-zero propagation angle corresponding
to each of the different colors of light.
22. A method of dual-direction light collimation, the method
comprising: collimating light in a vertical direction using a
vertical collimator to provide vertically collimated light; further
collimating the vertically collimated light in a horizontal
direction using a horizontal collimator located adjacent to an
output of the vertical collimator to produce dual-direction
collimated light that is both vertically collimated and
horizontally collimated; and creating a non-zero propagation angle
in the dual-direction collimated light, the non-zero propagation
angle being in a vertical plane corresponding to the vertical
direction.
23. The method of dual-direction light collimation of claim 22,
wherein the vertical collimator comprises an optical reflector
having a parabolic shape and a tilt angle, the tilt angle providing
the non-zero propagation angle of the dual-direction collimated
light, and wherein the horizontal collimator comprises another
optical reflector having another parabolic shape and spanning an
output aperture of the horizontal collimator to produce a uniform
distribution of the dual-direction collimated light across the
output aperture.
24. A method of three-dimensional (3D) electronic display operation
comprising the method of dual-direction light collimation of claim
22, the method of 3D electronic display operation further
comprising: guiding the dual-direction collimated light in a plate
light guide at the non-zero propagation angle; diffractively
coupling out a portion of the guided dual-direction collimated
light using a multibeam diffraction grating at a surface of the
plate light guide to produce a plurality of light beams directed
away from the plate light guide in a plurality of different
principal angular directions corresponding to directions of
different 3D views of a 3D electronic display; and modulating light
beams of the plurality of light beams using an array of light
valves, the modulated light beams forming 3D pixels of the 3D
electronic display in the 3D view directions.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation patent application of and
claims the benefit of priority to International Application No.
PCT/US2015/056529, filed Oct. 20, 2015, which claims priority from
U.S. Provisional Patent Application Ser. No. 62/214,978, filed Sep.
5, 2015, the entirely of which are incorporated by reference
herein.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] N/A
BACKGROUND
[0003] Electronic displays are a nearly ubiquitous medium for
communicating information to users of a wide variety of devices and
products. Among the most commonly found electronic displays are the
cathode ray tube (CRT), plasma display panels (PDP), liquid crystal
displays (LCD), electroluminescent displays (EL), organic light
emitting diode (OLED) and active matrix OLEDs (AMOLED) displays,
electrophoretic displays (EP) and various displays that employ
electromechanical or electrofluidic light modulation (e.g., digital
micromirror devices, electrowetting displays, etc.). In general,
electronic displays may be categorized as either active displays
(i.e., displays that emit light) or passive displays (i.e.,
displays that modulate light provided by another source). Among the
most obvious examples of active displays are CRTs, PDPs and
OLEDs/AMOLEDs. Displays that are typically classified as passive
when considering emitted light are LCDs and EP displays. Passive
displays, while often exhibiting attractive performance
characteristics including, but not limited to, inherently low power
consumption, may find somewhat limited use in many practical
applications given the lack of an ability to emit light.
[0004] To overcome the applicability limitations of passive
displays associated with light emission, many passive displays are
coupled to an external light source. The coupled light source may
allow these otherwise passive displays to emit light and function
substantially as an active display. Examples of such coupled light
sources are backlights. Backlights are light sources (often
so-called `panel` light sources) that are placed behind an
otherwise passive display to illuminate the passive display. For
example, a backlight may be coupled to an LCD or an EP display. The
backlight emits light that passes through the LCD or the EP
display. The light emitted by the backlight is modulated by the LCD
or the EP display and the modulated light is then emitted, in turn,
from the LCD or the EP display. Often backlights are configured to
emit white light. Color filters are then used to transform the
white light into various colors used in the display. The color
filters may be placed at an output of the LCD or the EP display
(less common) or between the backlight and the LCD or the EP
display, for example.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] Various features of examples and embodiments accordance with
the principles described herein may be more readily understood with
reference to the following detailed description taken in
conjunction with the accompanying drawings, where like reference
numerals designate like structural elements, and in which:
[0006] FIG. 1 illustrates a graphical view of angular components
{.theta., .phi.} of a light beam having a particular principal
angular direction, according to an example of the principles
describe herein.
[0007] FIG. 2A illustrates a perspective view of a dual-direction
optical collimator in an example, according to an embodiment of the
principles described herein.
[0008] FIG. 2B illustrates a top view of a dual-direction optical
collimator in an example, according to an embodiment of the
principles described herein.
[0009] FIG. 2C illustrates a cross sectional view of the
dual-direction optical collimator illustrated in FIG. 2B, according
to an embodiment of the principles described herein.
[0010] FIG. 3 illustrates a schematic representation of an optical
reflector having a tilt in an example, according to an embodiment
consistent with the principles described herein.
[0011] FIG. 4A illustrates a top view of a dual-direction optical
collimator in an example, according to an embodiment consistent
with the principles described herein.
[0012] FIG. 4B illustrates a top view of a dual-direction optical
collimator in an example, according to another embodiment
consistent with the principles described herein.
[0013] FIG. 4C illustrates a top view of a dual-direction optical
collimator in an example, according to yet another embodiment
consistent with the principles described herein.
[0014] FIG. 5A illustrates a top view of a backlight in an example,
according to an embodiment consistent with the principles of the
principles described herein.
[0015] FIG. 5B illustrates a cross sectional view of a backlight in
an example, according to an embodiment consistent with the
principles of the principles described herein.
[0016] FIG. 5C illustrates a cross sectional view of a portion of a
backlight in an example, according to an embodiment consistent with
the principles described herein.
[0017] FIG. 6A illustrates a cross sectional view of a portion of a
backlight with a multibeam diffraction grating in an example,
according to an embodiment consistent with the principles described
herein.
[0018] FIG. 6B illustrates a cross sectional view of a portion of a
backlight with a multibeam diffraction grating in an example,
according to another embodiment consistent with the principles
described herein.
[0019] FIG. 6C illustrates a perspective view of the backlight
portion of either FIG. 6A or FIG. 6B including the multibeam
diffraction grating in an example, according to an embodiment
consistent with the principles described herein.
[0020] FIG. 7 illustrates a block diagram of a three-dimensional
(3D) electronic display in an example, according to an embodiment
of the principles described herein.
[0021] FIG. 8 illustrates a flow chart of a method of
dual-direction light collimation in an example, according to an
embodiment consistent with the principles described herein.
[0022] FIG. 9 illustrates a flow chart of a method of
three-dimensional (3D) electronic display operation in an example,
according to an embodiment consistent with the principles described
herein.
[0023] Certain examples have other features that are one of in
addition to and in lieu of the features illustrated in the
above-referenced figures. These and other features are detailed
below with reference to the above-referenced figures.
DETAILED DESCRIPTION
[0024] Embodiments and examples in accordance with the principles
described herein provide dual-direction collimation and display
backlighting using the dual-direction collimation. In particular,
embodiments of the principles described herein provide
dual-direction light collimation that includes collimating light
separately in a vertical direction and in a horizontal direction.
Moreover, in some embodiments, the light may be collimated in a
vertical direction followed by the vertically collimated light
being separately collimated in a horizontal direction. In addition,
dual-direction collimation described herein provides dual-direction
collimated light having a predetermined, non-zero propagation angle
in a vertical plane corresponding to the vertical direction.
[0025] According to various embodiments, the dual-direction
collimation is provided by a dual-direction collimator comprising a
vertical collimator (e.g., vertical collimating reflector) coupled
at an output to a horizontal collimator (e.g., horizontal
collimating reflector). Light from a light source (e.g., a
plurality of LEDs) may be coupled into the dual-direction
collimator for dual-direction collimation. According to some
embodiments, the dual-direction collimated light from the
dual-direction collimator may be coupled into a light guide (e.g.,
a plate light guide) of a backlight used in an electronic display.
For example, the backlight may be a grating-based backlight
including, but not limited to, a grating-based backlight having a
multibeam diffraction grating. In some embodiments, the electronic
display may be a three-dimensional (3D) electronic display used to
display 3D information, e.g., an autostereoscopic or `glasses free`
3D electronic display.
[0026] In particular, a 3D electronic display may employ a
grating-based backlight having an array of multibeam diffraction
gratings. The multibeam diffraction gratings may be used to couple
light from a light guide and to provide coupled-out light beams
corresponding to pixels of the 3D electronic display. For example,
the coupled-out light beams may have different principal angular
directions (also referred to as `the differently directed light
beams`) from one another. According to some embodiments, these
differently directed light beams produced by the multibeam
diffraction grating may be modulated and serve as 3D pixels
corresponding to 3D views of the `glasses free` 3D electronic
display to display 3D information. In these embodiments, the
dual-direction collimation provided by the dual-direction
collimator may be used to produce output dual-direction collimated
light that is substantially uniform (i.e., without striping) within
the light guide. In turn, uniform illumination of the multibeam
diffraction gratings may be provided, in accordance with the
principles described herein.
[0027] Herein, a `light guide` is defined as a structure that
guides light within the structure using total internal reflection.
In particular, the light guide may include a core that is
substantially transparent at an operational wavelength of the light
guide. In various examples, the term `light guide` generally refers
to a dielectric optical waveguide that employs total internal
reflection to guide light at an interface between a dielectric
material of the light guide and a material or medium that surrounds
that light guide. By definition, a condition for total internal
reflection is that a refractive index of the light guide is greater
than a refractive index of a surrounding medium adjacent to a
surface of the light guide material. In some embodiments, the light
guide may include a coating in addition to or instead of the
aforementioned refractive index difference to further facilitate
the total internal reflection. The coating may be a reflective
coating, for example. The light guide may be any of several light
guides including, but not limited to, one or both of a plate or
slab guide and a strip guide.
[0028] Further herein, the term `plate` when applied to a light
guide as in a `plate light guide` is defined as a piece-wise or
differentially planar layer or sheet, which is sometimes referred
to as a `slab` guide. In particular, a plate light guide is defined
as a light guide configured to guide light in two substantially
orthogonal directions bounded by a top surface and a bottom surface
(i.e., opposite surfaces) of the light guide. Further, by
definition herein, the top and bottom surfaces are both separated
from one another and may be substantially parallel to one another
in at least a differential sense. That is, within any
differentially small region of the plate light guide, the top and
bottom surfaces are substantially parallel or co-planar.
[0029] In some embodiments, a plate light guide may be
substantially flat (i.e., confined to a plane) and so the plate
light guide is a planar light guide. In other embodiments, the
plate light guide may be curved in one or two orthogonal
dimensions. For example, the plate light guide may be curved in a
single dimension to form a cylindrical shaped plate light guide.
However, any curvature has a radius of curvature sufficiently large
to insure that total internal reflection is maintained within the
plate light guide to guide light.
[0030] According to various embodiments described herein, a
diffraction grating (e.g., a multibeam diffraction grating) may be
employed to scatter or couple light out of a light guide (e.g., a
plate light guide) as a light beam. Herein, a `diffraction grating`
is generally defined as a plurality of features (i.e., diffractive
features) arranged to provide diffraction of light incident on the
diffraction grating. In some examples, the plurality of features
may be arranged in a periodic or quasi-periodic manner. For
example, the plurality of features (e.g., a plurality of grooves in
a material surface) of the diffraction grating may be arranged in a
one-dimensional (1-D) array. In other examples, the diffraction
grating may be a two-dimensional (2-D) array of features. The
diffraction grating may be a 2-D array of bumps on or holes in a
material surface, for example.
[0031] As such, and by definition herein, the `diffraction grating`
is a structure that provides diffraction of light incident on the
diffraction grating. If the light is incident on the diffraction
grating from a light guide, the provided diffraction or diffractive
scattering may result in, and thus be referred to as, `diffractive
coupling` in that the diffraction grating may couple light out of
the light guide by diffraction. The diffraction grating also
redirects or changes an angle of the light by diffraction (i.e., at
a diffractive angle). In particular, as a result of diffraction,
light leaving the diffraction grating (i.e., diffracted light)
generally has a different propagation direction than a propagation
direction of the light incident on the diffraction grating (i.e.,
incident light). The change in the propagation direction of the
light by diffraction is referred to as `diffractive redirection`
herein. Hence, the diffraction grating may be understood to be a
structure including diffractive features that diffractively
redirects light incident on the diffraction grating and, if the
light is incident from a light guide, the diffraction grating may
also diffractively couple out the light from light guide.
[0032] Further, by definition herein, the features of a diffraction
grating are referred to as `diffractive features` and may be one or
more of at, in and on a surface (i.e., wherein a `surface` refers
to a boundary between two materials). The surface may be a surface
of a plate light guide. The diffractive features may include any of
a variety of structures that diffract light including, but not
limited to, one or more of grooves, ridges, holes and bumps, and
these structures may be one or more of at, in and on the surface.
For example, the diffraction grating may include a plurality of
parallel grooves in a material surface. In another example, the
diffraction grating may include a plurality of parallel ridges
rising out of the material surface. The diffractive features
(whether grooves, ridges, holes, bumps, etc.) may have any of a
variety of cross sectional shapes or profiles that provide
diffraction including, but not limited to, one or more of a
sinusoidal profile, a rectangular profile (e.g., a binary
diffraction grating), a triangular profile and a saw tooth profile
(e.g., a blazed grating).
[0033] By definition herein, a `multibeam diffraction grating` is a
diffraction grating that produces coupled-out light that includes a
plurality of light beams. Further, the light beams of the plurality
produced by a multibeam diffraction grating have different
principal angular directions from one another, by definition
herein. In particular, by definition, a light beam of the plurality
has a predetermined principal angular direction that is different
from another light beam of the light beam plurality as a result of
diffractive coupling and diffractive redirection of incident light
by the multibeam diffraction grating. The light beam plurality may
represent a light field. For example, the light beam plurality may
include eight light beams that have eight different principal
angular directions. The eight light beams in combination (i.e., the
light beam plurality) may represent the light field, for example.
According to various embodiments, the different principal angular
directions of the various light beams are determined by a
combination of a grating pitch or spacing and an orientation or
rotation of the diffractive features of the multibeam diffraction
grating at points of origin of the respective light beams relative
to a propagation direction of the light incident on the multibeam
diffraction grating.
[0034] In particular, a light beam produced by the multibeam
diffraction grating has a principal angular direction given by
angular components {.theta., .phi.}, by definition herein. The
angular component .phi. is referred to herein as the `elevation
component` or `elevation angle` of the light beam. The angular
component .phi. is referred to as the `azimuth component` or
`azimuth angle` of the light beam, herein. By definition, the
elevation angle .theta. is an angle in a vertical plane (e.g.,
perpendicular to a plane of the multibeam diffraction grating)
while the azimuth angle .theta. is an angle in a horizontal plane
(e.g., parallel to the multibeam diffraction grating plane). FIG. 1
illustrates the angular components {.theta., .phi.} of a light beam
10 having a particular principal angular direction, according to an
example of the principles describe herein. In addition, the light
beam 10 is emitted or emanates from a particular point, by
definition herein. That is, by definition, the light beam 10 has a
central ray associated with a particular point of origin within the
multibeam diffraction grating. FIG. 1 also illustrates the light
beam point of origin O. An example propagation direction of
incident light is illustrated in FIG. 1 using a bold arrow 12.
[0035] According to various embodiments, characteristics of the
multibeam diffraction grating and features thereof, may be used to
control one or both of the angular directionality of the light
beams and a wavelength or color selectivity of the multibeam
diffraction grating with respect to one or more of the light beams.
The characteristics that may be used to control the angular
directionality and wavelength selectivity include, but are not
limited to, one or more of a grating length, a grating pitch
(feature spacing), a shape of the features, a size of the features
(e.g., groove or ridge width), and an orientation of the grating.
In some examples, the various characteristics used for control may
be characteristics that are local to a vicinity of the point of
origin of a light beam.
[0036] According to various embodiments described herein, the light
coupled out of the light guide by the diffraction grating (e.g., a
multibeam diffraction grating) represents a pixel of an electronic
display. In particular, the light guide having a multibeam
diffraction grating to produce the light beams of the plurality
having different principal angular directions may be part of a
backlight of or used in conjunction with an electronic display such
as, but not limited to, a `glasses free` three-dimensional (3D)
electronic display (also referred to as a multiview or
`holographic` electronic display or an autostereoscopic display).
As such, the differently directed light beams produced by coupling
out guided light from the light guide using the multibeam
diffractive grating may be or represent `3D pixels` of the 3D
electronic display. Further, the 3D pixels correspond to different
3D views or 3D view angles of the 3D electronic display.
[0037] Herein a `collimating` reflector is defined as a reflector
having a curved shape that is configured to collimate light
reflected by the collimating reflector (e.g., a collimating
mirror). For example, the collimating reflector may have a
reflecting surface characterized by a parabolic curve or shape. In
another example, the collimating reflector may comprise a shaped
parabolic reflector. By `shaped parabolic` it is meant that a
curved reflecting surface of the shaped parabolic reflector
deviates from a `true` parabolic curve in a manner determined to
achieve a predetermined reflection characteristic (e.g., a degree
of collimation). In some embodiments, the collimating reflector may
be a continuous reflector (i.e., having a substantially smooth,
continuous reflecting surface), while in other embodiments, the
collimating reflector may comprise a Fresnel reflector or Fresnel
mirror that provides light collimation. According to various
embodiments, an amount of collimation provided by the collimating
reflector may vary in a predetermined degree or amount from one
embodiment to another. Further, the collimating reflector may be
configured to provide collimation in one or both of two orthogonal
directions (e.g., a vertical direction and a horizontal direction).
That is, the collimating reflector may include a parabolic shape in
one or both of two orthogonal directions, according to some
embodiments.
[0038] Herein, a `light source` is defined as a source of light
(e.g., an apparatus or device that emits light). For example, the
light source may be a light emitting diode (LED) that emits light
when activated. Herein, a light source may be substantially any
source of light or optical emitter including, but not limited to,
one or more of a light emitting diode (LED), a laser, an organic
light emitting diode (OLED), a polymer light emitting diode, a
plasma-based optical emitter, a fluorescent lamp, an incandescent
lamp, and virtually any other source of light. The light produced
by a light source may have a color or may include a particular
wavelength of light. As such, a `plurality of light sources of
different colors` is explicitly defined herein as a set or group of
light sources in which at least one of the light sources produces
light having a color, or equivalently a wavelength, that differs
from a color or wavelength of light produced by at least one other
light source of the light source plurality. Moreover, the
`plurality of light sources of different colors` may include more
than one light source of the same or substantially similar color as
long as at least two light sources of the plurality of light
sources are different color light sources (i.e., produce a color of
light that is different between the at least two light sources).
Hence, by definition herein, a plurality of light sources of
different colors may include a first light source that produces a
first color of light and a second light source that produces a
second color of light, where the second color differs from the
first color.
[0039] Further, as used herein, the article `a` is intended to have
its ordinary meaning in the patent arts, namely `one or more`. For
example, `a grating` means one or more gratings and as such, `the
grating` means `the grating(s)` herein. Also, any reference herein
to `top`, `bottom`, `upper`, `lower`, `up`, `down`, `front`, back',
`first`, `second`, `left` or `right` is not intended to be a
limitation herein. Herein, the term `about` when applied to a value
generally means within the tolerance range of the equipment used to
produce the value, or may mean plus or minus 10%, or plus or minus
5%, or plus or minus 1%, unless otherwise expressly specified.
Further, the term `substantially` as used herein means a majority,
or almost all, or all, or an amount within a range of about 51% to
about 100%. Moreover, examples herein are intended to be
illustrative only and are presented for discussion purposes and not
by way of limitation.
[0040] According to some embodiments, a dual-direction optical
collimator is provided. FIG. 2A illustrates a perspective view of a
dual-direction optical collimator 100 in an example, according to
an embodiment of the principles described herein. FIG. 2B
illustrates a top view of a dual-direction optical collimator 100
in an example, according to an embodiment of the principles
described herein. FIG. 2C illustrates a cross sectional view of a
portion of the dual-direction optical collimator 100 illustrated in
FIG. 2B, according to an embodiment of the principles described
herein. In particular, the cross section illustrated in FIG. 2C is
indicated in FIG. 2B. According to various embodiments, the
dual-direction optical collimator 100 is configured to collimate
received light in or with respect to at least two different
directions.
[0041] In particular, as illustrated in FIGS. 2A and 2C, the
dual-direction optical collimator 100 is configured to receive
light 102. In some examples, the light 102 received by the
dual-direction optical collimator 100 may be substantially
uncollimated light. For example, the light 102 may be provided by
and thus be received from a substantially uncollimated light source
(not illustrated). In another example, the received light 102 may
be partially collimated light (e.g., provided by a light source
that includes a lens or using some other partial collimation
means).
[0042] The dual-direction optical collimator 100 illustrated in
FIGS. 2A-2C is configured to collimate the received light 102 and
to provide collimated light 104 at an output of the dual-direction
optical collimator 100 (e.g., an output port, an output plane, an
output surface, etc.). The collimated light 104 provided at the
dual-direction optical collimator output is collimated or at least
substantially collimated in at least two directions, according to
various embodiments. As such, the collimated light 104 may be
referred to as `dual-direction` collimated light 104.
[0043] In particular, the dual-direction collimated light 104 is
collimated in two directions that are generally orthogonal to a
propagation direction of the dual-direction collimated light 104,
by definition herein. Further, by definition, the two collimation
directions are mutually orthogonal to one another. For example, the
dual-direction collimated light 104 may be collimated in or with
respect to a horizontal direction (e.g., in an x-y plane) and also
in or with respect to a vertical direction (e.g., a z-direction).
Herein the dual-direction collimated light 104 provided by the
dual-direction optical collimator 100 is referred to as being both
horizontally collimated and vertically collimated or equivalently
collimated in both a horizontal direction and vertical direction by
way of example and not limitation (i.e., the horizontal and
vertical directions may be determined relative to an arbitrary
reference frame, for example).
[0044] Further according to various embodiments, the dual-direction
optical collimator 100 is configured to provide the dual-direction
collimated light 104 at a non-zero propagation angle at the
dual-direction optical collimator output. For example, the non-zero
propagation angle may be an angle relative to or defined with
respect to a horizontal plane of the dual-direction optical
collimator 100. As defined herein, the `non-zero propagation angle`
is an angle relative to a plane (e.g., the horizontal or x-y plane)
or equivalently to a surface of a light guide, as described herein.
In some examples, the non-zero propagation angle of the
dual-direction collimated light 104 may be between about ten (10)
degrees and about fifty (50) degrees or, in some examples, between
about twenty (20) degrees and about forty (40) degrees, or between
about twenty-five (25) degrees and about thirty-five (35) degrees.
For example, the non-zero propagation angle may be about thirty
(30) degrees. In other examples, the non-zero propagation angle may
be about 20 degrees, or about 25 degrees, or about 35 degrees.
Further, according to some embodiments, the non-zero propagation
angle is both greater than zero and less than a critical angle of
total internal reflection within a light guide, as described
below.
[0045] As illustrated in FIGS. 2A-2C, the dual-direction optical
collimator 100 comprises a vertical collimator 110. The vertical
collimator 110 is configured to collimate light in a vertical
direction (i.e., in a z-direction). FIG. 2C illustrates a cross
sectional view of the vertical collimator 110 in an example
according to an embodiment of the principles herein. Further FIG.
2C illustrates the received light 102 as an arrow entering the
vertical collimator 110, e.g., at an input of the vertical
collimator 110. Light exiting the vertical collimator 110 as
`vertically` collimated light 104' after being collimated in the
vertical direction is also illustrated in FIG. 2C as another arrow
(i.e., dashed-line arrow in both FIGS. 2B-2C). According to various
embodiments, the vertical collimator 110 may comprise any of a
variety of collimator types including, but not limited to, a
collimating optical reflector, a collimating lens and a diffraction
grating configured to provide collimation.
[0046] In particular, as illustrated in FIG. 2C, the vertical
collimator 110 may comprise an optical reflector 112 having a
parabolic shape. The parabolic shape of the optical reflector 112
is configured to provide the vertical-direction collimation. In
some embodiments, the parabolic shape of the optical reflector 112
may have a so-called `purely` parabolic shape. In other
embodiments, the parabolic shape of the optical reflector 112 may
be adjusted, optimized or otherwise `shaped` to enhance or tweak
collimation characteristics of the optical reflector 112. For
example, the parabolic shape of the optical reflector 112 may be
tweaked as a shaped parabolic reflector to optimize vertical
collimation of light 102 received from a light source that includes
some directional distortion or partial (albeit non-ideal or
undesirable) collimation. As such, the optical reflector 112 may be
referred to as a `shaped` parabolic reflector 112. Further, the
shaped parabolic reflector 112 may be shaped or shape-optimized in
both the vertical direction (e.g., to control or optimize vertical
collimation) and the horizontal direction. For example, in addition
to being shaped in the vertical direction, the shaped parabolic
reflector 112 may be shape-optimized in the horizontal direction to
determine or provide control of a distribution (e.g., a width or a
spread) of the vertically collimated light 104' in the horizontal
direction. Nevertheless, for ease of discussion herein, the optical
reflector 112 of the vertical collimator 110 is generally referred
to as having `a parabolic shape,` whether the optical reflector 112
has a purely parabolic shape or is a shaped parabolic reflector
112, unless an explicit distinction is necessary for proper
understanding.
[0047] Further, in some embodiments (e.g., as illustrated in FIG.
2C), the optical reflector 112 of the vertical collimator 110 may
include a tilt angle (i.e., the optical reflector 112 may be tilted
at the tilt angle). The tilt angle may be configured to provide a
non-zero propagation angle of the vertically collimated light 104',
and by extension, to provide the non-zero propagation angle (or at
least a portion thereof) of the dual-direction collimated light
104. In other words, the optical reflector 112 itself may be
tilted. In some examples, the tilt angle may be provided by a
`shaping` of the shaped parabolic reflector 112 instead of or in
addition to an actual or physical tilting of the optical reflector
112 itself. In yet another example, the tilt angle may be provided
by a shift in a location of the light source that provides the
received light 102 relative to the focus of a parabola of the
optical reflector 112. In addition, when another type of collimator
(e.g., a collimating lens or a diffraction grating) is employed,
the other collimator type may be `tilted` to provide the tilt
angle, according to various embodiments.
[0048] FIG. 3 illustrates a schematic representation of an optical
reflector having a tilt in an example, according to an embodiment
consistent with the principles described herein. In particular, as
illustrated in FIG. 3, the optical reflector 112 is tilted downward
at a tilt angle corresponding to or configured to provide
vertically collimated light 104' having a non-zero propagation
angle .theta.'. FIG. 3 also illustrates a dashed line representing
a horizontal plane H from which the non-zero propagation angles
.theta.' are defined. Further, FIG. 3 illustrates using another
(e.g., bold) dashed line an example optical reflector 112' that is
not tilted to show the tilt angle .theta.' of the tilted optical
reflector 112. Note, as illustrated, the tilt angle .theta.' of the
tilted optical reflector 112 and the non-zero propagation angle
.theta.' are equal to one another, by example and not limitation.
Light 102 received from a light source in a vicinity of a focus F
of the optical reflector 112 is illustrated in FIG. 3 as a pair of
diverging light rays (i.e., solid line arrows) incident on the
optical reflector 112. Similarly, the vertically collimated light
104' exiting the optical reflector 112 is illustrated as a pair of
rays (i.e., dashed line arrows) that are substantially parallel to
one another. Further, the vertically collimated light rays 104' are
illustrated having the non-zero propagation angle .theta.' provided
by the optical reflector tilt angle.
[0049] Referring again to FIGS. 2A-2B, the dual-direction optical
collimator 100 further comprises a horizontal collimator 120. The
horizontal collimator 120 is configured to collimate light in the
horizontal direction (i.e., in a x-y plane, as illustrated) that is
substantially orthogonal to the vertical direction (i.e.,
z-direction, as illustrated). According to various embodiments, the
horizontal collimator 120 is located to receive the vertically
collimated light 104' from the vertical collimator 110. In
particular, as illustrated in FIGS. 2A-2B, the horizontal
collimator 120 is located adjacent to an output of the vertical
collimator 110. The horizontal collimator 120 is configured to
horizontally collimate the vertically collimated light 104' from
the vertical collimator 110 to provide the dual-direction
collimated light 104 at an output of the dual-direction optical
collimator 100.
[0050] FIG. 2B illustrates a top view of the horizontal collimator
120 depicting the vertically collimated light 104' as light rays
(i.e., as dashed line arrows) exiting the vertical collimator 110
and impinging on the horizontal collimator 120. Light exiting the
horizontal collimator 120 as the dual-direction collimated light
104 (i.e., both horizontally and vertically collimated) is
illustrated as a plurality of substantially parallel rays
propagating away from the horizontal collimator 120. According to
various embodiments, the horizontal collimator 120 may comprise any
of a variety of collimator types including, but not limited to, a
collimating optical reflector, a collimating lens and a diffraction
grating configured to provide collimation.
[0051] In particular, as illustrated in FIGS. 2A and 2B, the
horizontal collimator 120 may comprise an optical reflector 122
having a parabolic shape. The parabolic shape of the optical
reflector 122 is configured to provide the horizontal-direction
collimation. As with the optical reflector 112 of the vertical
collimator 110, in some embodiments, the parabolic shape of the
optical reflector 122 of the horizontal collimator 120 may have a
so-called `purely` parabolic shape. In other embodiments, the
parabolic shape may be adjusted, optimized or otherwise `shaped` to
enhance or tweak collimation characteristics of the optical
reflector 122. For example, the parabolic shape of the optical
reflector 122 may be tweaked as a shaped parabolic reflector to
optimize horizontal collimation of the vertically collimated light
104' received from the vertical collimator 110. In particular, the
tweaked, shaped parabolic optical reflector 122 may be optimized to
horizontally collimate some directional distortion or other
non-ideal or undesirable collimation artifacts in the vertically
collimated light 104'. As such, the optical reflector 122 of the
horizontal collimator 120 may be referred to as a `shaped`
parabolic reflector 122. For ease of discussion herein, the optical
reflector 122 of the horizontal collimator 120 is generally
referred to as having `a parabolic shape,` whether the optical
reflector 122 has a purely parabolic shape or is a shaped parabolic
reflector 122, unless an explicit distinction is necessary for
proper understanding.
[0052] Further, in some embodiments (not illustrated), the optical
reflector 122 of the horizontal collimator 120, may include a tilt
angle. In some embodiments, the tilt angle may be configured to
provide the non-zero propagation angle of the dual-direction
collimated light 104. In other embodiments, the tilt angle may be
configured to provide a portion of the non-zero propagation angle
to augment a portion of the non-zero propagation angle provided by
the vertical collimator 110. In other words, the optical reflector
122 itself or equivalently a parabolic shape of the optical
reflector 122, may be tilted. In some examples, the tilt angle may
be provided by a `shaping` of the shaped parabolic reflector 122
instead of or in addition to an actual or physical tilting of the
optical reflector 122. In yet another example, the tilt angle may
be provided by a shift in a location of the vertical collimator 110
relative to the focus of a parabola of the optical reflector 122 of
the horizontal collimator 120. In addition, when another type of
collimator (e.g., a collimating lens or a diffraction grating) is
employed, the other collimator type may be `tilted` to provide the
tilt angle, according to various embodiments.
[0053] As illustrated in FIGS. 2A and 2B, the optical reflector 122
of the horizontal collimator 120 may be configured to substantially
span an output aperture of the dual-direction optical collimator
100. In some embodiments, the horizontal collimator 120 is
configured to provide the dual-direction collimated light 104
having a substantially uniform distribution across the output
aperture. In particular, the optical reflector 122 may span the
output aperture to provide the substantially uniform distribution
of the dual-direction collimated light 104.
[0054] In some embodiments, the optical reflector 122 of the
horizontal collimator 120 may comprise a plurality of
sub-reflectors 122'. In particular, the sub-reflectors 122' may be
configured in combination to substantially span the output aperture
of the dual-direction optical collimator 100. According to various
embodiments, each sub-reflector 122' may comprise a
parabolic-shaped reflective surface. For example, the optical
reflector 122 may be a Fresnel reflector.
[0055] FIG. 4A illustrates a top view of a dual-direction optical
collimator 100 in an example, according to an embodiment consistent
with the principles described herein. In particular, FIG. 4A
illustrates the optical reflector 122 of the horizontal collimator
120 as a Fresnel reflector having a plurality of sub-reflectors
122'. The vertical collimator 110 is illustrated in FIG. 4A along
with the dual-direction collimated light 104.
[0056] FIG. 4B illustrates a top view of a dual-direction optical
collimator 100 in an example, according to another embodiment
consistent with the principles described herein. In particular,
FIG. 4B illustrates the dual-direction optical collimator 100
comprising a horizontal collimator 120 having a plurality of
sub-reflectors 122' along with a plurality of vertical collimators
110. As illustrated in FIG. 4B, a first sub-reflector 122'a of the
horizontal collimator sub-reflector plurality is configured to
receive vertically collimated light 104' from a first vertical
collimator 110a of the vertical collimator plurality located at a
first edge 120a of the horizontal collimator 120. Further, a second
sub-reflector 122'b of the horizontal collimator sub-reflector
plurality is configured to receive the vertically collimated light
104' from a second vertical collimator 110b of the vertical
collimator plurality located at a second edge 120b of the
horizontal collimator 120. The second edge 120b is opposite to the
first edge 120a in the horizontal plane corresponding to the
horizontal direction, as illustrated. Also illustrated in FIG. 4B,
example rays of the dual-direction collimated light 104 are
illustrated exiting the output aperture of the dual-direction
optical collimator 100.
[0057] FIG. 4C illustrates a top view of a dual-direction optical
collimator 100 in an example, according to yet another embodiment
consistent with the principles described herein. In particular,
FIG. 4C illustrates the dual-direction optical collimator 100
comprising a horizontal collimator 120 having a plurality of
sub-reflectors 122' along with a plurality of vertical collimators
110. As illustrated in FIG. 4C, a first sub-reflector 122'a of the
sub-reflector plurality is configured to receive vertically
collimated light 104' from a second vertical collimator 110b of the
vertical collimator plurality that is located at a second edge 120b
of the horizontal collimator 120 opposite to the first
sub-reflector 122'a. Further, a second sub-reflector 122'b of the
sub-reflector plurality is configured to receive vertically
collimated light 104' from a first vertical collimator 110a of the
vertical collimator plurality that is located at the first edge
120a opposite to the second sub-reflector 122'b, as illustrated in
FIG. 4C. In other words, the sub-reflectors 122'a, 122'b in FIG. 4C
are configured to receive the vertically collimated light 104' from
respective opposite edges of the horizontal collimator 120, as
compared to the dual-direction optical collimator 100 illustrated
in FIG. 4B. Moreover, the dual-direction optical collimator 100 of
FIG. 4C is configured to provide the dual-direction collimated
light 104 to the output aperture of the dual-direction optical
collimator 100, as further illustrated in FIG. 4C.
[0058] Although not explicitly illustrated, the dual-direction
optical collimator 100 may include a sub-reflector plurality having
more than two sub-reflectors 122'. Similarly, the vertical
collimator 110 may comprise a plurality of vertical collimators 110
that includes more than two individual vertical collimators 110.
For example, each of the two sub-reflectors 122', 122'a, 122'b of
FIGS. 4A-4C may be further divided into two or more sub-reflectors
(e.g., a plurality of sub-sub-reflectors). Further, the plurality
of vertical collimators 110 including more than two individual
vertical collimators 110 may be used to provide vertically
collimated light 104' to the more than two sub-reflectors (e.g.,
one vertical collimator for each sub-sub-reflector). Moreover,
different vertical collimators 110 may be employed for different
colors of received light 102 to provide different colors of
vertically collimated light 104' to the optical reflector 122
(i.e., including sub-reflectors 122') of the horizontal collimator
120.
[0059] In particular, any of a number of different
sub-reflector/vertical collimator configurations may be employed
without departing from the scope of the principles described
herein. Moreover, the use of various different
sub-reflector/vertical collimator configurations may facilitate
scanning of the dual-direction collimated light 104 across the
output aperture as well as may provide increased brightness (e.g.,
using multiple light sources) of the dual-direction collimated
light 104, according to some embodiments.
[0060] In some embodiments, one or both of the vertical collimator
110 and the horizontal collimator 120 may comprise a substantially
optically transparent material. In addition, portions of the
dual-direction optical collimator 100 between the vertical
collimator 110 and the horizontal collimator 120 as well as between
the horizontal collimator 120 and the output aperture of the
dual-direction optical collimator 100 may comprise the
substantially optically transparent material, in some embodiments.
The optically transparent material may include or be made up of any
of a variety of dielectric materials including, but not limited to,
one or more of various types of glass (e.g., silica glass,
alkali-aluminosilicate glass, borosilicate glass, etc.) and
substantially optically transparent plastics or polymers (e.g.,
poly(methyl methacrylate) or `acrylic glass`, polycarbonate, etc.).
For example, one or both of the vertical collimator 110 and the
horizontal collimator 120 may comprise an optically transparent
material formed to have parabolic-shaped surface. The
parabolic-shaped surface, in turn, may be metalized or otherwise
coated with a reflective material to provide the optical reflectors
112, 122, for example. Reflective materials used to coat the
parabolic-shaped surface(s) may include, but are not limited to,
aluminum, chromium, nickel, silver and gold, for example. Further,
the vertical collimator 110 may be integral to and comprise a
material of the horizontal collimator 120, according to some
embodiments. FIG. 2A illustrates by way of example and not
limitation the dual-direction optical collimator 100 having
integral vertical and horizontal collimators 110, 120 formed from a
common, optically transparent material.
[0061] In some embodiments, the material of the dual-direction
optical collimator 100 may serve as a light guide to guide light by
total internal reflection. The light guide may guide light between
the vertical collimator 110 and the horizontal collimator 120,
according to some embodiments. FIG. 2C illustrates vertically
collimated light 104' being reflected at an interface between the
material of the dual-direction optical collimator 100 adjacent to
the vertical collimator 110 and another material (e.g., air)
outside of the material using total internal reflection. The
illustrated reflection represents guiding of the vertically
collimated light 104' within a portion of the dual-direction
optical collimator 100 illustrated in FIG. 2C from the optical
reflector 112 of the vertical collimator 110 in a direction toward
the horizontal collimator 120 (not shown in FIG. 2C). In some
embodiments (e.g., as illustrated in FIG. 2A), the material also
may extend from the horizontal collimator 120 (e.g., the optical
reflector 122) to the output aperture. The material is configured
as a light guide to guide the vertically collimated light 104' and
the dual-direction collimated light 104 to the output aperture.
[0062] According to some embodiments of the principles described
herein, a backlight employing dual-direction collimation is
provided. FIG. 5A illustrates a top view of a backlight 200 in an
example, according to an embodiment consistent with the principles
of the principles described herein. FIG. 5B illustrates a cross
sectional view of a backlight 200 in an example, according to an
embodiment consistent with the principles of the principles
described herein. As illustrated in FIGS. 5A-5B, the backlight 200
comprises a dual-direction optical collimator 210.
[0063] In some embodiments, the dual-direction optical collimator
210 may be substantially similar to the dual-direction optical
collimator 100 described above. In particular, the dual-direction
optical collimator 210 comprises a vertical collimator 212 and a
horizontal collimator 214 each of which may be substantially
similar to respective ones of the vertical collimator 110 and the
horizontal collimator 120 of the dual-direction optical collimator
100. For example, dashed outlines associated with the
dual-direction optical collimator 210 in FIG. 5A may resemble the
dual-direction optical collimator 100 illustrated in FIG. 4B.
According to various embodiments, the dual-direction optical
collimator 210 is configured to receive light 202, illustrated in
FIG. 5B (e.g., from a light source 230, described below), and
provide dual-direction collimated light 204 at an output of the
dual-direction optical collimator 210. Further, the dual-direction
collimated light 204 is provided having a non-zero propagation
angle relative to the horizontal x-y plane.
[0064] As illustrated in FIGS. 5A-5B, the backlight 200 further
comprises a plate light guide 220 coupled (e.g., optically coupled)
to the output of the dual-direction optical collimator 210. The
plate light guide 220 is configured to receive and to guide the
dual-direction collimated light 204 at the non-zero propagation
angle, as illustrated in FIG. 5B. According to various embodiments,
the plate light guide 220 is further configured to emit a portion
of the guided, dual-direction collimated light 204 from a surface
of the plate light guide 220. In FIG. 5B, emitted light 206 is
illustrated as a plurality of rays (arrows) extending away from the
plate light guide surface.
[0065] In some embodiment, the plate light guide 220 may be a slab
or plate optical waveguide comprising an extended, planar sheet of
substantially optically transparent, dielectric material. The
planar sheet of dielectric material is configured to guide the
dual-direction collimated light 204 from the dual-direction optical
collimator 210 as a guided light beam 204 using total internal
reflection. The dielectric material may have a first refractive
index that is greater than a second refractive index of a medium
surrounding the dielectric optical waveguide. The difference in
refractive indices is configured to facilitate total internal
reflection of the guided light beam 204 according to one or more
guided modes of the plate light guide 220, for example.
[0066] According to various examples, the substantially optically
transparent material of the plate light guide 220 may include or be
made up of any of a variety of dielectric materials including, but
not limited to, one or more of various types of glass (e.g., silica
glass, alkali-aluminosilicate glass, borosilicate glass, etc.) and
substantially optically transparent plastics or polymers (e.g.,
poly(methyl methacrylate) or `acrylic glass`, polycarbonate, etc.).
In some examples, the plate light guide 220 may further include a
cladding layer on at least a portion of a surface (e.g., one or
both of the top surface and the bottom surface) of the plate light
guide 220 (not illustrated). The cladding layer may be used to
further facilitate total internal reflection, according to some
examples.
[0067] In some embodiments, (e.g., as illustrated in FIG. 5A), the
plate light guide 220 may be integral to the dual-direction optical
collimator 210. In particular, the plate light guide 220 and the
dual-direction optical collimator 210 may be formed from and thus
comprise the same material. For example, the plate light guide 220
may be an extension of a light guide extending or connecting
between a horizontal collimator and an output aperture of the
dual-direction optical collimator 210. In other embodiments (e.g.,
as illustrated in FIG. 5B), the dual-direction optical collimator
210 and the plate light guide 220 are separate and coupling (e.g.,
one or both of optical coupling and mechanical coupling) thereof is
provided by a glue or adhesive layer, another interface material or
even air between the output aperture and an input of the plate
light guide 220. For example, the dual-direction optical collimator
210 may comprise a polymer or plastic material and the plate light
guide 220 may comprise glass. The dual-direction optical collimator
210 and the plate light guide 220 may be affixed to one another
using a suitable adhesive layer 222 (e.g., an optically matched
glue), for example as illustrated in FIG. 5B.
[0068] According to some embodiments, the backlight 200 may further
comprise a light source 230. The light source 230 is configured to
provide light to the dual-direction optical collimator 210. In
particular, the light source 230 is located adjacent to (e.g.,
below, as illustrated in FIG. 5B) the vertical collimator 212 of
the dual-direction optical collimator 210 and is configured to
provide the light 202 to an input of the vertical collimator 212 as
the received light 202. In various embodiments, the light source
230 may comprise substantially any source of light including, but
not limited to, one or more light emitting diodes (LEDs). In some
examples, the light source 230 may comprise an optical emitter
configured produce a substantially monochromatic light having a
narrowband spectrum denoted by a particular color. In particular,
the color of the monochromatic light may be a primary color of a
particular color space or color model (e.g., a red-green-blue (RGB)
color model).
[0069] In some embodiments, the light source 230 may comprise a
plurality of different optical sources configured to provide
different colors of light (i.e., `different color` optical
sources). The different optical sources may be offset from one
another, for example. The offset of the different optical sources
may be configured to provide different, color-specific, non-zero
propagation angles of the dual-direction collimated light 204
corresponding to each of the different colors of light, according
to some embodiments. In particular, the offset may add an
additional non-zero propagation angle component to the non-zero
propagation angle provided by the dual-direction collimator 210,
for example.
[0070] FIG. 5C illustrates a cross sectional view of a portion of a
backlight 200 in an example, according to an embodiment consistent
with the principles of the principles described herein. For
example, the portion of the backlight 200 illustrated in FIG. 5C
may be substantially similar to the dual-direction collimator
portion illustrated in FIG. 2C. In particular, FIG. 5C illustrates
a portion of the backlight 200 that includes the vertical
collimator 212 along with the light source 230 comprising a
plurality of different optical sources. As illustrated in FIG. 5C,
the plurality of different optical sources of the light source 230
includes a first optical source 232 configured to provide light of
a first color (e.g., red light), a second optical source 234
configured to provide light of a second color (e.g., green), and a
third optical source 236 configured to provide light of a third
color (e.g., blue). For the example, the first, second and third
optical sources 232, 234, 236 of the light source 230 may
respectively comprise a red LED, a green LED and a blue LED. Each
of the different optical sources 232, 234 and 236 of the light
source 230 is offset from one another, as illustrated.
[0071] Specifically, the different optical sources 232, 234 and 236
are illustrated in FIG. 5C as being laterally offset from one
another in a propagation direction of the vertical collimated light
204'. The offset, in turn, results in the light 202 produced by the
different optical sources 232, 234 and 236 having different,
non-zero propagation angles upon exiting the vertical collimator
212 as vertically collimated light 204'. Since each of the
illustrated optical sources 232, 234 and 236 produces light of a
different color, the vertically collimated light 204' comprises
three different light beams, each light beam having a different,
color-specific, non-zero propagation angle, as illustrated in FIG.
5C. Note, in FIG. 5C, different line types (e.g., dashed, solid,
etc.) indicate the different colors of light 202, 204'.
[0072] According to some embodiments (e.g., as illustrated in FIG.
5B), the backlight 200 may further comprise a multibeam diffraction
grating 240 at a surface of the plate light guide 220. The
multibeam diffraction grating 240 is configured to diffractively
couple out a portion of the guided, dual-direction collimated light
204 from the plate light guide 220 as a plurality of light beams
206. The plurality of light beams 206 (i.e., the plurality of rays
(arrows) illustrated in FIG. 5B) represents the emitted light 206.
In various embodiments, a light beam 206 of the light beam
plurality has a principal angular direction that is different from
principal angular directions of other light beams 206 of the light
beam plurality.
[0073] In some embodiments, the multibeam diffraction grating 240
is a member of or is arranged in an array of multibeam diffraction
gratings 240. In some embodiments, the backlight 200 is a backlight
of a three-dimensional (3D) electronic display and the principal
angular direction of the light beam 206 corresponds to a view
direction of the 3D electronic display.
[0074] FIG. 6A illustrates a cross sectional view of a portion of a
backlight 200 with a multibeam diffraction grating 240 in an
example, according to an embodiment consistent with the principles
described herein. FIG. 6B illustrates a cross sectional view of a
portion of a backlight 200 with a multibeam diffraction grating 240
in an example, according to another embodiment consistent with the
principles described herein. FIG. 6C illustrates a perspective view
of the backlight portion of either FIG. 6A or FIG. 6B including the
multibeam diffraction grating 240 in an example, according to an
embodiment consistent with the principles described herein. The
multibeam diffraction grating 240 illustrated in FIG. 6A comprises
grooves in a surface of the plate light guide 220, by way of
example and not limitation. FIG. 6B illustrates the multibeam
diffraction grating 240 comprising ridges protruding from the plate
light guide surface.
[0075] As illustrated in FIGS. 6A-6B, the multibeam diffraction
grating 240 is a chirped diffraction grating. In particular, the
diffractive features 240a are closer together at a first end 240'
of the multibeam diffraction grating 240 than at a second end
240''. Further, the diffractive spacing d of the illustrated
diffractive features 240a varies from the first end 240' to the
second end 240''. In some embodiments, the chirped diffraction
grating of the multibeam diffraction grating 240 may have or
exhibit a chirp of the diffractive spacing d that varies linearly
with distance. As such, the chirped diffraction grating of the
multibeam diffraction grating 240 may be referred to as a `linearly
chirped` diffraction grating.
[0076] In another embodiment, the chirped diffraction grating of
the multibeam diffraction grating 240 may exhibit a non-linear
chirp of the diffractive spacing d. Various non-linear chirps that
may be used to realize the chirped diffraction grating include, but
are not limited to, an exponential chirp, a logarithmic chirp or a
chirp that varies in another, substantially non-uniform or random
but still monotonic manner. Non-monotonic chirps such as, but not
limited to, a sinusoidal chirp or a triangle or sawtooth chirp, may
also be employed. Combinations of any of these types of chirps may
also be used in the multibeam diffraction grating 240.
[0077] As illustrated in FIG. 6C, the multibeam diffraction grating
240 includes diffractive features 240a (e.g., grooves or ridges)
in, at or on a surface of the plate light guide 220 that are both
chirped and curved (i.e., the multibeam diffraction grating 240 is
a curved, chirped diffraction grating, as illustrated). The guided
light beam 204 guided in the plate light guide 220 has an incident
direction relative to the multibeam diffraction grating 240 and the
plate light guide 220, as illustrated by a bold arrow in FIGS.
6A-6C. Also illustrated is the plurality of coupled-out or emitted
light beams 206 pointing away from the multibeam diffraction
grating 240 at the surface of the plate light guide 220. The
illustrated light beams 206 are emitted in a plurality of different
predetermined principal angular directions. In particular, the
different predetermined principal angular directions of the emitted
light beams 206 are different in both azimuth and elevation (e.g.,
to form a light field).
[0078] According to various examples, both the predefined chirp of
the diffractive features 240a and the curve of the diffractive
features 240a may be responsible for a respective plurality of
different predetermined principal angular directions of the emitted
light beams 206. For example, due to the diffractive feature curve,
the diffractive features 240a within the multibeam diffraction
grating 240 may have varying orientations relative to an incident
direction of the guided light beam 204 within the plate light guide
220. In particular, an orientation of the diffractive features 240a
at a first point or location within the multibeam diffraction
grating 240 may differ from an orientation of the diffractive
features 240a at another point or location relative to the guided
light beam incident direction. With respect to the coupled-out or
emitted light beam 206, an azimuthal component of the principal
angular direction {.theta., .phi.} of the light beam 206 may be
determined by or correspond to the azimuthal orientation angle
.phi..sub.f of the diffractive features 240a at a point of origin
of the light beam 206 (i.e., at a point where the incident guided
light beam 204 is coupled out). As such, the varying orientations
of the diffractive features 240a within the multibeam diffraction
grating 240 produce different light beams 206 having different
principal angular directions {.theta., .phi.}, at least in terms of
their respective azimuthal components .phi..
[0079] In particular, at different points along the curve of the
diffractive features 240a, an `underlying diffraction grating` of
the multibeam diffraction grating 240 associated with the curved
diffractive features 240a has different azimuthal orientation
angles .phi..sub.f. By `underlying diffraction grating`, it is
meant that diffraction gratings of a plurality of non-curved
diffraction gratings in superposition yield the curved diffractive
features 240a of the multibeam diffraction grating 240. Thus, at a
given point along the curved diffractive features 240a, the curve
has a particular azimuthal orientation angle .phi..sub.f that
generally differs from the azimuthal orientation angle .phi..sub.f
at another point along the curved diffractive features 240a.
Further, the particular azimuthal orientation angle .phi..sub.f
results in a corresponding azimuthal component of a principal
angular direction {.theta., .phi.} of a light beam 206 emitted from
the given point. In some examples, the curve of the diffractive
features 240a (e.g., grooves, ridges, etc.) may represent a section
of a circle. The circle may be coplanar with the light guide
surface. In other examples, the curve may represent a section of an
ellipse or another curved shape, e.g., that is coplanar with the
plate light guide surface.
[0080] In other embodiments, the multibeam diffraction grating 240
may include diffractive features 240a that are `piecewise` curved.
In particular, while the diffractive feature 240a may not describe
a substantially smooth or continuous curve per se, at different
points along the diffractive feature 240a within the multibeam
diffraction grating 240, the diffractive feature 240a still may be
oriented at different angles with respect to the incident direction
of the guided light beam 204. For example, the diffractive feature
240a may be a groove including a plurality of substantially
straight segments, each segment having a different orientation than
an adjacent segment. Together, the different angles of the segments
may approximate a curve (e.g., a segment of a circle), according to
various embodiments. In yet other examples, the diffractive
features 240a may merely have different orientations relative to
the incident direction of the guided light at different locations
within the multibeam diffraction grating 240 without approximating
a particular curve (e.g., a circle or an ellipse).
[0081] In some embodiments, the grooves or ridges that form the
diffractive features 240a may be etched, milled or molded into the
plate light guide surface. As such, a material of the multibeam
diffraction gratings 240 may include the material of the plate
light guide 220. As illustrated in FIG. 6B, for example, the
multibeam diffraction grating 240 includes ridges that protrude
from the surface of the plate light guide 220, wherein the ridges
may be substantially parallel to one another. In FIG. 6A (and FIG.
5B), the multibeam diffraction grating 240 includes grooves that
penetrate the surface of the plate light guide 220, wherein the
grooves may be substantially parallel to one another. In other
examples (not illustrated), the multibeam diffraction grating 240
may comprise a film or layer applied or affixed to the light guide
surface. The plurality of light beams 206 in different principal
angular directions provided by the multibeam diffraction gratings
240 are configured to form a light field in a viewing direction of
an electronic display. In particular, the backlight 200 employing
dual-direction collimation is configured to provide information,
e.g., 3D information, corresponding to pixels of an electronic
display.
[0082] In accordance with some embodiments of the principles
described herein, a three-dimensional (3D) electronic display is
provided. FIG. 7 illustrates a block diagram of a three-dimensional
(3D) electronic display 300 in an example, according to an
embodiment of the principles described herein. According to various
embodiments, the 3D electronic display 300 is configured to produce
modulated, directional light comprising light beams having
different principal angular directions and, in some embodiments,
also having a plurality of different colors. For example, the 3D
electronic display 300 may provide or generate a plurality of
different light beams 306 directed out and away from the 3D
electronic display 300 in different predetermined principal angular
directions (e.g., as a light field). Further, the different light
beams 306 may include light beams 306 of or having different colors
of light. In turn, the light beams 306 of the plurality may be
modulated as modulated light beams 306' to facilitate the display
of information including color information (e.g., when the light
beams 306 are color light beams).
[0083] In some embodiments, the modulated light beams 306' having
different predetermined principal angular directions form a
plurality of pixels of the 3D electronic display 300. In some
examples, the 3D electronic display 300 may be a so-called `glasses
free` 3D color electronic display (e.g., a multiview, `holographic`
or autostereoscopic display) in which the modulated light beams
306' correspond to pixels associated with different `views` of the
3D electronic display 300. Modulated light beams 306' are
illustrated using dashed line arrows 306' in FIG. 7, while the
different light beams 306 prior to modulation are illustrated as
solid line arrows, by way of example.
[0084] The 3D electronic display 300 illustrated in FIG. 7
comprises a dual-direction optical collimator 310 (abbreviated as
`Dual-Dir. Coll.` in FIG. 7). The dual-direction optical collimator
310 is configured to provide dual-direction collimated light having
both vertical collimation and horizontal collimation. In
particular, the vertical and horizontal collimation is with respect
to a vertical direction (e.g., z-direction) or a vertical plane
(e.g., y-z plane) and a horizontal direction (e.g., x-direction) or
a horizontal plane (x-y plane) of the dual-direction optical
collimator 310. Further, the dual-direction optical collimator 310
is configured to provide the dual-direction collimated light at a
non-zero propagation angle relative to the horizontal plane of the
dual-direction collimator 310.
[0085] In some embodiments, the dual-direction optical collimator
310 is substantially similar to the above-described dual-direction
optical collimator 100. In particular, the dual-direction
collimator 310 comprises a vertical collimator and a horizontal
collimator. The horizontal collimator is located adjacent to an
output of the vertical collimator. Further, the vertical collimator
may be substantially similar to the vertical collimator 110 and the
horizontal collimator may be substantially similar to the
horizontal collimator 120 described with respect to the
dual-direction optical collimator 100, according to some
embodiments.
[0086] For example, the vertical collimator of the dual-direction
collimator 310 may comprise an optical reflector having a parabolic
shape and a tilt angle. The tilt angle may be configured to
determine the non-zero propagation angle of the dual-direction
collimated light at an output of the dual-direction optical
collimator. Further, for example, the horizontal collimator of the
dual-direction collimator 310 may comprise an optical reflector
having a parabolic shape. The optical reflector of the horizontal
collimator may be configured to substantially span an output
aperture of the dual-direction optical collimator and to provide
the dual-direction collimated light with a substantially uniform
distribution across the output aperture, for example. In addition,
the dual-direction collimator 310 may comprise vertical and
horizontal collimators arranged in various other configurations
including sub-reflectors and multiple vertical collimators, e.g.,
as described above with respect to the vertical collimator 110 and
horizontal collimator 120 of the dual-direction optical collimator
100.
[0087] As illustrated in FIG. 7, the 3D electronic display 300
further comprises a plate light guide 320. The plate light guide
320 is configured to guide the dual-direction collimated light as a
guided light beam at the non-zero propagation angle. In particular,
the guided light beam may be guided at the non-zero propagation
angle relative to a surface (e.g., one or both of a top surface and
a bottom surface) of the plate light guide 320. The surface may be
parallel to the horizontal plane in some embodiments. According to
some embodiments, the plate light guide 320 may be substantially
similar to the plate light guide 220 described above with respect
to the backlight 200.
[0088] According to various embodiments and as illustrated in FIG.
7, the 3D electronic display 300 further comprises an array of
multibeam diffraction gratings 330 located at a surface of the
plate light guide 320. According to some embodiments, a multibeam
diffraction grating 330 of the array may be substantially similar
to the multibeam diffraction grating 240 described above with
respect to the backlight 200. In particular, a multibeam
diffraction grating 330 of the array is configured to diffractively
couple out a portion of the guided light beam as plurality of
coupled-out light beams having different principal angular
directions and representing the light beams 306. Moreover, the
different principal angular directions of light beams 306 coupled
out by the multibeam diffraction grating 330 correspond to
different 3D views of the 3D electronic display 300, according to
various embodiments. In some embodiments, the multibeam diffraction
grating 330 comprises a chirped diffraction grating having curved
diffractive features. In some embodiments, a chirp of the chirped
diffraction grating is a linear chirp.
[0089] In some embodiments, the 3D electronic display 300 (e.g., as
illustrated in FIG. 7) further comprises a light source 340
configured to provide light to an input of the dual-direction
optical collimator 310. In some embodiments, the light source 340
may be substantially similar to the light source 230 of the
backlight 200, described above. In particular, the light source 340
may comprise a plurality of different light emitting diodes (LEDs)
configured to provide different colors of light (referred to as
`different colored LEDs` for simplicity of discussion). In some
embodiments, the different colored LEDs may be offset (e.g.,
laterally offset) from one another. The offset of the different
colored LEDs is configured to provide different, color-specific,
non-zero propagation angles of the dual-direction collimated light
from the dual-direction optical collimator 310. Further, a
different, color-specific, non-zero propagation angle may
correspond to each of the different colors of light provided by the
light source 340.
[0090] In some embodiments (not illustrated), the different colors
of light may comprise the colors red, green and blue of a
red-green-blue (RGB) color model. Further, the plate light guide
320 may be configured to guide the different colors as light beams
at different color-dependent propagation angles within the plate
light guide 320. For example, a first guided color light beam
(e.g., a red light beam) may be guided at a first color-dependent
propagation angle, a second guided color light beam (e.g., a green
light beam) may be guided at a second color-dependent propagation
angle, and a third guided color light beam (e.g., a blue light
beam) may be guided at a third color-dependent propagation angle,
according to some embodiments.
[0091] As illustrated in FIG. 7, the 3D electronic display 300 may
further comprise a light valve array 350. According to various
embodiments, the light valve array 350 is configured to modulate
the coupled-out light beams 306 of the light beam plurality as the
modulated light beams 306' to form or serve as the 3D pixels
corresponding to the different 3D views of the 3D electronic
display 300. In some embodiments, the light valve array 350
comprises a plurality of liquid crystal light valves. In other
embodiments, the light valve array 350 may comprise another light
valve including, but not limited to, an electrowetting light valve,
an electrophoretic light valves, a combination thereof, or a
combination of liquid crystal light valves and another light valve
type, for example.
[0092] In accordance with other embodiments of the principles
described herein, a method of dual-direction light collimation is
provided. FIG. 8 illustrates a flow chart of a method 400 of
dual-direction light collimation in an example, according to an
embodiment consistent with the principles described herein. As
illustrated in FIG. 8, the method 400 of dual-direction light
collimation comprises collimating 410 light in a vertical direction
using a vertical collimator to provide vertically collimated light.
In some embodiments, the vertical collimator is substantially
similar to the vertical collimator 110 described above with respect
to the dual-direction optical collimator 100. For example, the
vertical collimator used in collimating 410 light may comprise an
optical reflector having a parabolic shape.
[0093] The method 400 of dual-direction light collimation further
comprises further collimating 420 the vertically collimated light
in a horizontal direction using a horizontal collimator located
adjacent to an output of the vertical collimator to produce
dual-direction collimated light that is both vertically collimated
and horizontally collimated. In some embodiments, the horizontal
collimator is substantially similar to the horizontal collimator
120 described above with respect to the dual-direction optical
collimator 100. For example, the horizontal collimator used in
further collimating 420 the vertically collimated light may
comprise another optical reflector having another parabolic shape.
In some embodiments, the horizontal collimator optical reflector
may substantially span an output aperture of the horizontal
collimator to produce a substantially uniform distribution of the
dual-direction collimated light across the output aperture.
[0094] The method 400 of dual-direction light collimation
illustrated in FIG. 8 further comprises creating 430 a non-zero
propagation angle in the dual-direction collimated light, wherein
the non-zero propagation angle is in a vertical plane corresponding
to the vertical direction (or equivalently is an angle relative to
a horizontal plane). The non-zero propagation angle may be
substantially similar to the non-zero propagation angle described
above with respect to the dual-direction optical collimator 100,
for example. In particular, in some embodiments the non-zero
propagation angle may be provided by a tilt angle of the optical
reflector of one or both of the vertical collimator and the
horizontal collimator.
[0095] In accordance with yet other embodiments of the principles
described herein, a method of three-dimensional (3D) electronic
display operation is provided. FIG. 9 illustrates a flow chart of a
method 500 of 3D electronic display operation in an example,
according to an embodiment consistent with the principles described
herein. As illustrated in FIG. 9, the method 500 of 3D electronic
display operation comprises providing 510 dual-direction collimated
light having a non-zero propagation angle. According to various
embodiments, the dual-direction collimated light may be provided
510 using a dual-direction collimator. The dual-direction
collimator may be substantially similar to the dual-direction
optical collimator 100 described above. In some embodiments, the
dual-direction collimated light may be provided 510 according to
the method 400 of dual-direction light collimation, described
above. For example, providing 510 dual-direction collimated light
may employ a vertical collimator followed by a horizontal
collimator at an output of the vertical collimator.
[0096] The method 500 of 3D electronic display operation further
comprises guiding 520 the dual-direction collimated light in a
plate light guide. In particular, the dual-direction collimated
light is guided 520 at the non-zero propagation angle within the
plate light guide. According to some embodiments, the plate light
guide may be substantially similar to the plate light guide 220 of
the backlight 200, as described above.
[0097] The method 500 of 3D electronic display operation of FIG. 9
further comprises diffractively coupling out 530 a portion of the
guided dual-direction collimated light using a multibeam
diffraction grating to produce a plurality of light beams.
According to some embodiments, the multibeam diffraction grating is
located at a surface of the plate light guide. According to various
embodiments, diffractively coupling out 530 the guided
dual-direction collimated light portion is configured to provide
the plurality of light beams directed away from the plate light
guide in a plurality of different principal angular directions. In
particular, the plurality of different principal angular directions
corresponds to directions of different 3D views of a 3D electronic
display. According to some embodiments, the multibeam diffraction
grating is substantially similar to the multibeam diffraction
grating 240 and the diffractively coupled-out 530 light beams of
the light beam plurality correspond to the light beams 206,
described above with respect to the backlight 200 or the light
beams 306 of the 3D electronic display 300.
[0098] According to various embodiments, the method 500 of 3D
electronic display operation illustrated in FIG. 9 further
comprises modulating 540 light beams of the plurality of light
beams using an array of light valves. The modulated 540 light beams
form 3D pixels of the 3D electronic display in the 3D view
directions, according to various embodiments. In some embodiments,
the array of light valves may be substantially similar to the light
valve array 350 described above with respect to the 3D electronic
display 300.
[0099] In some embodiments (not illustrated), the method 500 of 3D
electronic display operation further comprises providing light to
be dual-direction collimated. For example, the light may be
non-collimated light provided to a dual-direction optical
collimator, such as the dual-direction collimator that may be used
in providing 510 dual-direction collimated light. The light may be
provided using a light source at an input of the vertical
collimator, for example. Further, the light source may be
substantially similar to the light source 230 described above with
respect to the backlight 200, in some embodiments.
[0100] Thus, there have been described examples of a dual-direction
optical collimator, a backlight and a 3D electronic display that
employ a dual-direction optical collimator, a method of
dual-direction collimation and a method of 3D electronic display
operation that employs dual-direction collimation. It should be
understood that the above-described examples are merely
illustrative of some of the many specific examples that represent
the principles described herein. Clearly, those skilled in the art
can readily devise numerous other arrangements without departing
from the scope as defined by the following claims.
* * * * *